October 28, 2014
Exam 3 is on Thursday, December 4th (final class period).
Exam 4 is on Friday, December 12th, 3-5p.
Term project is due Tuesday, December 9th. Email your HTML file to jelsner@fsu.edu.
No class next week Tuesday (Nov 4) and Thursday (Nov 6). I will be attending the AMS conference on severe local storms in Madison, WI. Use this time to get started on your term project.
Tornado and supercells thunderstorms.
Rotating column of air between a cloud and the ground. A funnel is visible rotation below the base of the cloud but the rotation is not reaching the ground.
Most (80%) tornadoes (EF0 & EF1) have winds weaker than 50 m/s (100 mph). These tornadoes account for 5% of all tornado deaths.
Strong (EF2 & EF3) tornadoes have winds from 50 to 73 m/s. Violent (EF4 & EF5 ) tornadoes have winds exceeding 73 m/s and are quite rare (about 1% of all tornadoes). The most violent tornadoes have winds exceeding 100 m/s.
A tornado is assigned a single EF (Enhanced Fujita scale) damage rating based on the worst damage within the path.
Damage path length/width by EF category
A supercell thunderstorm is a rotating thunderstorm called a mesocyclone.
The updraft of rising air near the ground weakens when the air from the rear flank downdraft (RFD) catches up to the air from the forward flank downdraft (FFD).
This stretches the rotating updraft and speeds the rotation.
Vortex stretching is not always enough to create a tornado (only 30% of all supercells produce tornadoes).
What else?